Scientific name: Sclerotinia Homoeocarpa
Identification
An infected area of turf consists of circular spots, each typically some 25mm in diameter, however sizes do vary. These spots can join together to form larger infected areas, however, the area generally maintains a spotted appearance. The infected grass is usually a light straw colour.
Closer inspection of a leaf can reveal either
- an upper bleached part with a lower green part or
- a central green part bordered with a lower and higher bleached part or
- a central bleached part bordered by green leaf either side.
Where the leaf is partly bleached a black line may separate it from the green part of the leaf.
This disease is not a common one of turf in the UK.
Main grasses affected
Common on Slender creeping red fescue (Festuca rubra ssp litoralis & F. rubra ssp pruinosa);
Uncommon on Strong creeping red fescue (Festuca rubra ssp rubra);
Rarely detrimental to Chewing's fescue (Festuca nigrescens).
Conditions favourable to the disease
- Low nutrient levels, especially nitrogen;
- Warm, especially humid weather;
- Poor air circulation;
- Surface moisture and waterlogged conditions;
- Damaged grass tissue;
- Sea washed turf which was historically used on bowling greens;
- Similar conditions to red thread and typically attacks at a similar time.
Control measures
- Maintain adequate nitrogen inputs;
- Increase nitrogen levels;
- Remove dew early in the morning;
- Keep the soil well aerated;
- Reduce thatch layers - both depth and density of them;
- Box off and remove clippings;
- Improve air circulation around the area: Consider thinning hedges, trees etc., removing overhanging branches;
- Use more resistant cultivars where available;
- Ensure mowers have sharp cutting blades and are correctly set;
- Improve the drainage system.
Notes
The improvement in the cultivars of slender creeping red fescue over the past 20 years has produced cultivars that are less susceptible to dollar spot.
With the rapidly reducing use of sea-washed turf for bowling greens this has also helped reduce disease occurrence.
The first recorded attack of dollar spot on Chewing's fescue in the UK was in 1989 and was reported in the 1990 STRI research journal.
References
Anon, 'Turfgrass Seed 2001', The Sports Turf Research Institute, 2000
Baldwin, N.A., Turfgrass Pests and Diseases, Third Edition, STRI, 1990
Newell, A.J.; Baldwin, N.A. 'The occurrence of dollar spot on festuca rubra subspecies and cultivars', The Journal of the Sports Turf Research Institute, 1990, 115-119;
Reeves, P. 'An appreciation of slender creeping red fescue', The Groundsman, March 1996, 14;
Shildrick, J.P. 'Evaluation of red fescue cultivars, 1973-76: Part IV Trials under close mowing', The Journal of the Sports Turf Research Institute, 1977, 9-34;